This project evaluates the hypothesis that individual differences in infants' adrenocortical and behavioral reactivity to stress will adversely impact on their subsequent capacity for emotion regulation in frustration-producing and wariness-producing situations. Infants who are characterized as highly reactive to stress in early infancy are expected to have difficulty in emotion regulation at older ages. It is clear that infant emotion regulation also is influenced by differences in maternal behavior and in various family risk factors including marital discord, life stress, family hassles, and social support. Thus, the primary aim of this project is to examine the relation between early differences in infant stress reactivity and in maternal behavior and family risk and subsequent emotion regulation/dysregulation. The project will involve a longitudinal study at 6, 15, and 24 months of age. Cortisol and behavioral stress responses to stress will be examined at 6 and 15 months of age. Maternal responsivity and sensitivity to infant distress will be observed in reaction to a variety of different stressors at these two ages. The capacity for emotion regulation to frustration and wariness will be evaluated at 15 and 24 months of age. Martial discord and other family risk variables will be assessed at all three ages. These data will allow us to examine the role of early differences in infant reactivity and in maternal behavior and family risk on subsequent emotion regulation. Finally, cortisol response to the stress of the emotion regulation situations will be measured at 15 and 24 months of age. These data will allow us to assess the relation between early cortisol response to inoculation and subsequent cortisol response to emotional stress. An early difficulty in emotion regulation is likely to have profound consequences for later social relationships and might lead to future psychosocial problems. The results from this study will bear on the origins of individual differences in emotion regulation in infancy, and therefore will have some theoretical and practical importance for our understanding of early socioemotional development and functioning. The results will further our knowledge of the early antecedents of different patterns of emotion regulation/dysregulation that become apparent in early childhood.